1. Field of the Invention
The present invention generally relates to a centrifugal fan and, more particularly, to a centrifugal fan capable of drawing air via an axial air inlet as well as expelling air via a radial air outlet.
2. Description of the Related Art
Conventional cooling fans generally include axial fans and centrifugal fans. The axial fan has an axial air inlet and an axial air outlet opposite to the axial air inlet in an axial direction thereof. Air can be drawn into the axial fan via the axial air inlet and then expelled via the axial air outlet, providing a desired cooling function. The centrifugal fan has an axial air inlet in an axial direction and a radial air outlet in a radial direction thereof. Air can be drawn into the centrifugal fan via the axial air inlet and then expelled via the radial air outlet for cooling purposes.
Due to the fact that the axial fan drives air in the axial direction rather than in the radial direction during the cooling operation, the axial fan must be mounted on a top of a heat source (such as on a top face of a CPU of a computer) when installed in an electronic device, making it difficult to reduce the height of the electronic device.
In addition, since the centrifugal fan expels air in the radial air outlet, the centrifugal fan does not need to be mounted on a top of a heat source. As such, the centrifugal fan can be installed in various mini-sized electronic devices with limited interior spaces. However, since the interior space of the mini-sized electronic device is limited, some problems are encountered, as stated below.
First, the centrifugal fan has an unsatisfied cooling effect and a shortened service life. Specifically, if the axial air inlet of the centrifugal fan is too close to an inner wall of the electronic device (or to any interior structures of the electronic device) when the centrifugal fan is installed in the electronic device, air cannot be smoothly drawn into the fan via the axial air inlet, and noise easily results, affecting the cooling effect and shortening the, service life of the centrifugal fan.
Second, it is difficult to miniaturize the electronic device. Specifically, if the axial air inlet of the centrifugal fan is spaced from the inner wall of the electronic device (or spaced from any interior structure of the electronic device) by a large distance (i.e. larger than the proper distance) when the centrifugal fan is installed in the electronic device, the centrifugal fan tends to occupy a large space in the electronic device despite the fact that air can be smoothly drawn into the fan via the axial air inlet. As a result, the size of the electronic device cannot be reduced.